function loadScript(sScriptSrc, oCallback) {
    var oHead = document.getElementsByTagName('head')[0];
    var oScript = document.createElement('script');
    oScript.type = 'text/javascript';
    oScript.src = sScriptSrc;
    // most browsers
    oScript.onload = oCallback;
    // IE 6 & 7
    oScript.onreadystatechange = function() {
        if (this.readyState == 'complete') {
            oCallback();
        }
    }
    oHead.appendChild(oScript);
}